Can open models carry readable silent signals before they speak? Reproducing J-Lens Readouts on Kimi K3 & Qwen3.5-9B

This post details the application of the Jacobian Lens (J-Lens) technique to Kimi K3 and Qwen3.5-9B models hosted on Fireworks AI. It demonstrates how J-Lens can be used to probe the internal states of these models to identify 'silent signals'—vocabulary associated with the final output that appears before the model generates its response. The post describes experiments, including a 'Paired Copy Experiment' and extending tests to eight more episodes, to show that these silent signals reflect the model's intended focus even when the visible output is the same. It also discusses the challenges encountered, such as tokenizer limitations, and highlights the technical requirements for running such analyses.